背景:莱姆病是欧洲最常见的蜱传疾病,通常由afzelii疏螺旋体引起,它是由蓖麻蜱传播的。受感染蜱的流行率和丰度在时间和空间上波动,影响人类感染风险。啮齿动物是阿泽利氏芽孢杆菌的水库宿主,也是幼虫蜱的重要摄食宿主。在这里报道的研究中,我们研究了啮齿动物丰度的变化如何与蜱中的阿非泽利芽孢杆菌感染患病率相关,第二年若虫的密度(DON)和受感染若虫的密度(DIN)。我们进一步分析了受感染啮齿动物的丰度与若虫感染率(NIP)和DIN之间的关系。
方法:我们在芬兰的15个岛屿(10个小岛和5个大岛)上进行了一项结合实验和观察方法的研究。在所有的岛屿上,2019年夏季对蜱和啮齿动物进行了监测和采样,对蜱丰度的监测和采样持续到2020年春季。在十个小岛中的五个,捕获的啮齿动物被从岛上移除(“移除”岛),在其他五个小岛上,捕获的啮齿动物在标记和取样后被释放回诱捕地点(“对照”岛)。在五个大岛上,捕获的啮齿动物在标记和取样后被释放回诱捕地点。检查了若虫和啮齿动物样品中是否存在阿泽利氏芽孢杆菌。
结果:实验研究的结果表明,无论是处理(去除),2019年被感染啮齿动物的啮齿动物丰度指数和丰度指数与DON相关,NIP或DIN在2020年。根据观察性研究的数据,随着2019年啮齿动物丰度指数和受感染啮齿动物丰度指数的增加,2020年的NIP下降。然而,2020年的DIN与2019年的啮齿动物丰度指数或受感染啮齿动物的丰度指数无关。此外,在观察性研究中,2020年DON随着啮齿动物丰度指数的增加而增加。
结论:我们的结果表明,在蜱活动期间啮齿动物丰度低不足以减少疾病危害,因此,在自然生态系统中,清除啮齿动物可能不是可行的控制措施。
BACKGROUND: Lyme borreliosis is the most common tick-borne disease in Europe and is often caused by Borrelia afzelii, which is transmitted by Ixodes ricinus ticks. The prevalence and abundance of infected ticks fluctuate in time and space, influencing human infection risk. Rodents are reservoir hosts for B. afzelii and important feeding hosts for larval ticks. In the
study reported here, we examined how variation in rodent abundance is associated with B. afzelii infection prevalence in ticks, the density of nymphs (DON) and the density of infected nymphs (DIN) in the following year. We further analysed the relationships between the abundance of infected rodents and nymphal infection prevalence (NIP) and DIN.
METHODS: We conducted a
study that combined experimental and observational approaches on 15 islands (10 small islands and 5 large islands) in Finland. On all of the islands, ticks and rodents were monitored and sampled during the summer of 2019, with the monitoring of tick abundance and sampling continuing into the spring of 2020. On five of the 10 small islands, captured rodents were removed from the island (\"removal\" islands), and on the other five small islands, captured rodents were released back to the trapping site after marking and sampling (\"control\" islands). On the five large islands, captured rodents were released back to the trapping site after marking and sampling. The presence of B. afzelii from
nymph and rodent samples was examined.
RESULTS: The results of the experimental study showed that neither treatment (removal), rodent abundance index nor abundance index of infected rodents in 2019 was associated with DON, NIP or DIN in 2020. Based on data from the observational
study, the NIP in 2020 decreased with increasing rodent abundance index and abundance index of infected rodents in 2019. However, the DIN in 2020 was not associated with the rodent abundance index or the abundance index of infected rodents in 2019. In addition, in the observational
study, DON in 2020 increased with increasing rodent abundance index.
CONCLUSIONS: Our results suggest that low rodent abundance during the tick activity period is not sufficient for reducing the disease hazard and, hence, rodent removal may not be a feasible control measure in natural ecosystems.